1. Field of the Invention
This invention relates to the use of dimethyldiallylammonium chloride homopolymers as the active antimicrobial agent in disinfecting and/or preserving solutions for contact lenses.
2. Description of the Prior Art
This invention relates to disinfecting and preserving contact lenses, particularly soft contact lenses. When the term "soft contact lenses" is used herein, it is generally referring to those contact lenses which readily flex under small amounts of force and return to their original shaped when released from that force. Typically, soft contact lenses are formulated from poly(hydroxyethyl methacrylate) which has been, in the preferred formulations, crosslinked with ethylene glycol dimethacrylate. For convenience, this polymer is generally known as PHEMA. Soft contact lenses are also made from silicone polymers typically crosslinked with dimethyl polysiloxane. As is known in the art, conventional hard lenses, which cover only the cornea of the eye, usually consist of poly(methylmethacrylate) crosslinked with ethylene glycol dimethacrylate.
Hard contact lenses do not absorb appreciable amounts of water as do some soft contact lenses and thus the use of harsher disinfecting and cleaning agents does not create a problem in the hard contact lenses cleaning area. However, many hard lens disinfecting and preserving solutions contain benzalkonium chloride or chlorobutanol which may render the treated lenses hydrophobic, may not be stable in solution or lack compatibility with certain types of hard lenses, e.g., high silicone content. As is generally known, the users of soft contact lenses are warned against using solutions made for hard contact lenses since the materials in the solutions, as mentioned, may be absorbed or even concentrated by the soft contact lenses and may seriously damage the soft contact lenses or the eye of the user.
U.S. Pat. No. 3,288,770, G. B. Butler, discloses water soluble quaternary ammonium polymers including solid polymers of dimethyldiallylammonium chloride. These polymers are mentioned at column 10 as having utility as spinning aids for textile materials, antistatic agents for textile materials, bacteriostatic and fungistatic agents, wet strength improvement agents for papers and other textile aids, as accelerators for curing rubber and as curing agents for epoxy resins and as stabilization and regulation agents for particle size in suspension polymerization and surface active agents. Thereafter considerable discussion is given to the use of these polymers as flocculating agents.
U.S. Pat. No. 3,539,684, M. F. Hoover, discloses bactericidal effects of various homopolymers and copolymers of fatty quaternary diallylammonium compounds. The use of dimethyldiallylammonium chloride as a comonomer does not reduce the effectiveness of the polymerized fatty quaternary monomer. There is no suggestion or teaching that polymeric dimethyldiallylammonium chloride has bacterial activity or synergistic effect. The fatty quaternary polymers and copolymers are stated to be useful in treating circulating water systems and swimming pools and other bodies of stagnant water to inhibit algae and bacteria.
U.K. patent application No. 2,027,040A discloses the use of water soluble terpolymers of diallylamine quaternary salts as sterilizing agents for contact lenses. The application teaches that each of the three types of monomers must be present in order to obtain an effective eye care solution. The N-substituents for each class of monomers are respectively (A) low-low, e.g., dimethyl, (B) low-medium, e.g., methyloctyl and (C) low-higher, e.g., methyllauryl or methylcetyl, in molecular size; B:C being usually 5:1 to 0.333:1 (preferably 2:1 to 1:1) in weight ratio, and species less than 10,000 or preferably 20,000 m.w. usually being removed, have surprisingly effective sterilizing activity, e.g., against Candida while (a) not accumulating in soft contact lenses, whereby they can be used as an overnight, non-irritant, aqueous, sterilant solution at concentrations below 0.1 weight percent, e.g., 0.05 or less and (b) not penetrating skin or like membranes whereby aqueous formulations can be used as topical disinfectants without systemic side effects.